Positioning and Navigation (PN) of Martian rovers still faces challenges due to limited observations. In this paper, the PN feasibilities of Mars rovers based on a Gravity-aided Odometry (GO) system are proposed and investigated in terms of numeric simulations and a case study. Statistical features of the Mars gravity field are studied to evaluate the feature diversity of the background map. The Iterative Closest Point (ICP) algorithm is introduced to match gravity measurements with the gravitational map. The trajectories of Mars Exploration Rovers (MER) and Mars Gravity Map 2011 (MGM2011) are used to complete the experiments. Several key factors of GO including odometry errors, measurement uncertainties, and grid resolution of the map are investigated to evaluate their influences on the positioning ability of the system. Simulated experiments indicate that the GO method could provide an alternative positioning solution for Martian surface rovers.

In this study, satellite based pseudo-range measurements are integrated with accelerometer measurements made by six accelerometers located on the six faces of a cuboid, to independently measure the translational and rotational accelerations, and the pseudo-range. These measurements are then processed by an adaptive Unscented Kalman filter (UKF) to correct for the estimated errors and to obtain the required position and velocities at two independent locations. The relative position and velocity are then obtained by the application of standard vector identities. From these estimates, the position and velocity kinematics of prosthetic limbs and measurements of the joint angles, the true ambulatory position is estimated using a third independent UKF based estimator. The robotic limb joint offsets are assumed to be biased which are also estimated by the third UKF. The basic assumption is that the errors in the measurements are quite similar at the two locations and for this reason it is hypothesised that these errors would be reduced when the relative position and velocity were estimated. The results indicate that the steady-state ambulatory position error of the end-effector is reduced by more than 98%.

The correct ambiguity resolution between reference stations is the core issue of the whole Network Real-Time Kinematic (RTK) technology. Aimed at long fixed time and low reliability of the low elevation angle satellite ambiguity resolution during the initialisation of the Network RTK system, a three-step algorithm is proposed in this paper. Firstly, the double difference wide-lane ambiguities are fixed on the basis of the Melbourne-Wubbena (MW) method. Secondly, the double difference L1 carrier phase ambiguities of the high elevation angle satellites are fixed rapidly based on the ionosphere-free combination model. Thirdly, the corresponding ambiguities of the satellites with low elevation angles are solved with restrictions from the double difference tropospheric information, which is obtained from observations of the high elevation angle satellites. Based on this algorithm, an overall scheme of the ambiguity resolution during the initialisation process of the Network RTK system is designed. Results from Global Positioning System (GPS)/Globalnaya Navigatsionnaya Sputnikovaya Sistema (GLONASS) data demonstrate that the three-step algorithm can reduce the ill-posed problems of the observation model effectively. Moreover, the speed and accuracy performances of the ambiguity resolution for the low elevation angle satellites using the proposed algorithm are better than those of the conventional method.

The year 1952 is the fourth centenary of the birth of Sir Walter Ralegh. So far from being the great romantic of tradition Sir Walter was a hard-headed practical man, and the first Englishman to engage a scientific and technical expert to advise him on his colonizing enterprises. He brought the brilliant young mathematician Thomas Hariot, some eight years his junior, direct from Oxford to Durham House, his mansion in the Strand, where, setting his instruments up on the leads, Hariot laboured for years at improving observational technique and revising the Ephemerides. Meanwhile he gave instruction in navigation to the officers of Ralegh's ships, himself obtaining practical experience on the voyage to Virginia in 1585, when he was able to observe the seaman's difficulties and the errors to which he was prone. He had already by 1584 written a new Instruction Manual which he entitled Arcticon, but this is unfortunately lost. We have, nevertheless, an epitome of its contents, for Ralegh asked for a ‘refresher course’ on the eve of his departure for Guiana, which was to take place in February 1595, and Hariot's teaching notes in his own (very crabbed) handwriting, besides fair copies of the tables he drew up, are now at the British Museum.

The aim of this paper is to provide a collective overview of current state-of-the-art weather routeing and it is therefore intended to give a descriptive appraisal. Essentially the paper will concentrate upon the vessel route optimization procedures, data-handling techniques including the parameters necessary to implement the methods, the ship-resistance characteristics and the James speed performance curves.

Receiver Autonomous Integrity Monitoring (RAIM) provides an integrity service for Global Navigation Satellite Systems (GNSS). The conventional RAIM algorithm is based on the assumption of a single fault and typically uses the forward-backward method, which is based on the w-test or correlation analysis methods, to exclude the faults. It is suitable for single fault detection and exclusion, while it can lead to inefficiency, can be misleading and can even fail in the exclusion of multiple faults. To solve this problem, an improved method based on consensus voting of the w-test and correlation analysis methods is presented. To verify the performance of the improved method, tests using Global Positioning System (GPS)/BeiDou System (BDS) data have been carried out in comparison with the conventional methods in terms of false and correct faults exclusion rate and computational complexity in the case of a different number of faults. Results show that the improved method has almost the same correct exclusion rate compared to the conventional RAIM in the case of a single fault. It is worth noting that the improved method has a higher correct exclusion probability and computational efficiency as well as a lower possibility of false exclusion in the case of multiple faults.

Dead reckoning (also called path integration) is the process by which a navigating organism derives its current position relative to an Earthbound reference point from its own locomotion. Dead reckoning requires the continuous estimation of changes in direction and location through self-generated signals and the computation of position on the basis of these signals.

(i) Hymenopterous insects measure rotations and translations mainly with the help of optical references such as the Sun and translational visual flow. By contrast, mammals are able to estimate their position on the basis of purely ‘internal’ information; that is, signals generated in the vestibular system by inertial forces, somatosensory feedback, and efference copies (copies of central commands that control the performance of rotations and translations). Obviously, the assessment of the angular and linear components of locomotion is much more precise if it is assisted by external references than if this is not the case.

(ii) Only man-made dead reckoning systems yield precise position information through the twofold integration over time of inertial signals deriving from angular and linear acceleration. On the biological level, all species tested so far seem to rely on a simplified form of path ‘integration’: in certain test situations, arthropods and mammals (including humans) commit similar systematic errors. This suggests that species from unrelated taxa update position according to a similar algorithm.

This paper analyses for the first time the impact of new GPS signals on positioning accuracy for dynamic urban applications, taking bus operations as an example. The performance assessment addresses both code measurement precision and positioning accuracy. The former is based on signal-to-noise ratio and estimation of multipath and noise by a combination of code and carrier phase measurements. The impact on positioning accuracy is derived by comparing the performance achievable with the conventional single frequency GPS only positioning both relative to reference trajectories from the integration of carrier phase measurements with data from a high grade inertial measurement unit. The results show that L5 code measurements have the highest precision, followed by L1 C/A and L2C. In the positioning domain, there is a significant improvement in two-dimensional and three-dimensional accuracy from dual frequency code measurements over the single frequency measurements, of 39% and 48% respectively, enabling more bus operation services to be supported.

The ability of animals to find their way, without the benefit of mechanical or electronic aids to navigation, has fascinated humans for centuries. Relying on innate knowledge, coupled with the extraction of navigational data from the natural features of the universe, animals continually confound humans with their skills in locomotion. The magnetic compass, sun compass, strip maps, snapshots, target maps, temperature charts and star charts are known to feature in the overall animal navigation kit. Each species selects the most appropriate ‘map/chart’ and navigation kit for its environment.

Receiver Autonomous Integrity Monitoring (RAIM) is a method implemented within the receiver to protect users against satellite navigation system failures. For a receiver to execute a RAIM calculation, two conditions must be met: a minimum number of satellites and adequate satellite geometry. The non-existence of the minimum number of satellites (five) is referred to as a RAIM hole. Current regional and global RAIM availability studies use spatial (grid-based) and temporal sampling intervals driven by a trade-off between accuracy and computation workload. The implication of minimising computational load is that accuracy is compromised and potential RAIM holes remain un-sampled, with potential risk to safety. This paper proposes a direct and computationally efficient method (as opposed to the grid-based search approach) to predict RAIM holes. The method is based on the precise computation of satellite coverage (footprint) boundaries, the intersection points and analysis of the topology of the regions of intersection. Test results show that the proposed method is highly accurate and requires minimal computational load compared to the current approach.

Ship domain is an important theory in ship collision avoidance and an effective collision detection method. First, several classical ship domain models are used in experiments. The results show that the alarm rate is too high in busy waters, leading to greatly reduced practicality of the model. Potential collision risk cannot be detected effectively, especially for a ship with restricted manoeuvrability, which is usually regarded as an overtaken ship due to its navigation characteristics. Therefore, it is necessary to fully consider the interference of other ships to ships with limited manoeuvrability in an encounter situation. A novel ship domain model for ships with restricted manoeuvrability in busy waters is proposed. Considering the navigation characteristics of a ship with restricted manoeuvrability and the influence of the ship–ship effect, an algorithm to determine the boundary of the ship domain model is given by force and moment equations. AIS trajectory data of the North Channel of the Yangtze River Estuary are used to perform a comparative experiment, and four classical ship domain models are employed to perform comparative experiments. The results show that the alarm rates of the novel ship domain model are 7⋅608%, 15⋅131%, 55⋅785% and 7⋅608% lower than those of the other four classical models, and this outcome can effectively reduce the high false alarm rate produced by other models in this environment.

Array antenna beam forming has high potential to improve the performance of the global navigation satellite system (GNSS) in urban areas. However, the widespread application of array antennas for GNSS multipath mitigation is restricted by many factors, such as the complexity of the system, the computation load and conflicts between required performance, cost budget and limited room for the antenna placement. The scope of this work is triplicate. (1) The pre-correlation beam forming structure is first suggested for multipath mitigation to decrease the system complexity. (2) With the pre-correlation structure, the equivalence of adaptive beam forming to quiescent beam forming is revealed. Therefore, the computational load for beam forming is greatly decreased. (3) A theoretical model is established to link the benefits of beam forming with GNSS performance improvement in terms of pseudorange quality. The model can be used by industry to balance the aforementioned restrictions. Numerical results with different array settings are given, and a 2 × 2 rectangle array with $0.4\lambda $ element spacing is suggested as a cost-effective choice in GNSS positioning applications in urban canyon areas.

The objective of this paper is to illustrate a methodology for the enhancement of meteorological marine forecasts tailored to the needs of navigation. The study consists of two parts: (1) Theoretical background. Introduction to numerical models for weather forecasting used by meteorological centres. A review of the most reliable equations for prediction of intensity and direction of wind and sea state. In particular, reference is made to the tables for wind forecasting developed by R. Mayençon and A. Pezzoli and the equations for prediction of sea state obtained by K. Haselman and D. J. T. Carter in light of the JONSWAP experiment. (2) Practical application. Application of the methodology to a real-world example: a weather forecast elaborated by the Meteohydrological Laboratory at Dipartimento d'Idraulica Trasporti ed Infrastrutture Civili (DITIC) of the Polytechnic of Turin. The forecast was requested by the Consorzio Prada Challenge 2000 as a meteorological support for the training they held in the Tyrrhenian Sea for the next America's Cup series.

X-ray pulsar navigation is a promising technology for autonomous spacecraft navigation. The key measurement of pulsar navigation is the time delay (phase delay). There are various methods to estimate phase delay, but most of them have high computational complexities. In this paper, a new method for phase delay estimation is proposed, which is based on the time-shift property of Discrete Fourier Transformation (DFT). With this method, the time complexity can be greatly reduced. Also, a delta-function approximation can be used to further decrease the computational cost. Numerical simulation shows that the proposed method is effective for phase delay estimation, and the reduced complexity makes our method more suitable for on board implementation.

Precise control is a key factor in enabling Unmanned Underwater Vehicles (UUVs) to complete various underwater activities. The development of UUV control rules is mostly based on UUV dynamic models. However, such dynamic models contain unknown hydrodynamic parameters that need to be identified. This paper presents a new method, Laser Line Scanning for Hydrodynamic Parameter Identification (LSHPI), which integrates laser line scanning, decoupled dynamics, and evolutionary optimisation to identify the hydrodynamic parameters of an Autonomous Underwater Vehicle (AUV). In this research, laser images, seen from an on board camera's perspective and created using Open Graphics Library (OpenGL), were used to validate LSHPI's feasibility. The accuracy of the AUV positions and Euler angles obtained by the laser image-based methods were investigated for each decoupled One-Dimensional (1D) motion and the influence of other motion disturbances on the accuracy of the obtained AUV positions or Euler angles was also evaluated. In addition, the accuracy of the surge-related hydrodynamic parameters obtained by LSHPI was investigated under different motion disturbances. Based on the hydrodynamic parameter identification results under different motion disturbances, LSHPI's feasibility was successfully validated.

According to comprehensive theories of navigation, animals navigate by using two complementary strategies: (1) dead reckoning informs the subject in a continuous manner on its actual location with respect to an Earthbound or absolute coordinate system; while (2) long-term associations between particular landmarks and specific locations allow the animal to find its way within a familiar environment. If the subject structures familiar space as a system of interconnected places – the so-called ‘cognitive map’ – it may know through dead reckoning where it is located on its map and relate its route-based expectations to the actually perceived scenario of local cues.

The object of this paper is to present various practical solutions to the problems of inertia navigation in a descriptive rather than a mathematical form. Inertia navigation is an automatic bump of locality, a dead-reckoning device which, starting from a known point, seeks to find position. Other dead-reckoning devices measure speed, which is only relative to the fluid sea or air. Inertia navigation measures accelerations, which are absolute, and hence builds up a measure of speed. The accelerometer is, therefore, a good starting point for our survey.

In this paper the role of the helmsman in terms of man–machine systems theory, such as is frequently used in aerospace work is considered and the literature of the subject surveyed in so far as it relates to the control of seagoing vessels. Lieutenant-Commander Sutton is in the Control Engineering Department at the Royal Naval Engineering College, Plymouth, and Professor Towill is head of the Department of Mechanical Engineering at UWIST, Cardiff.